Origin and Significance of Non-Uniform Morphology in AFP Composites

Abstract

Employing automated fiber placement provides a high level of control over intricate layup designs, but it introduces irregular morphology due to fiber tow deposition effects, such as tow gaps and overlaps. A confluence of elements like squeeze flow, resin bleed-out, and non-linear deformation results in morphological variation on micro and macro levels. To delve into these complex, interrelated phenomena, we developed a multiphysics finite element framework designed to simulate compaction behavior specifically around areas with fiber tow gaps. This structure integrates chemo-rheological and flow-compaction analyses. Within the compaction analysis, we incorporated a visco-hyperelastic constitutive model. This model is characterized by anisotropic tensorial prepreg viscosity, a feature that is dependent on the resin cure degree and local fiber orientation and volume fraction. Our approach considers the impact of resin bleed-out into the gap region, which results in the formation of a complex, non-uniform resin-rich pocket. The predicted morphology from the proposed finite element simulation agreed with the observed morphology in cured sample with staggered fiber tow gaps.